Formic Acid-Assisted Selective Hydrogenolysis of 5-Hydroxymethylfurfural to 2,5-Dimethylfuran over Bifunctional Pd Nanoparticles Supported on N-Doped Mesoporous Carbon.

Biomass-derived 5-hydroxymethylfurfural (HMF) is regarded as one of the most promising platform chemicals to produce 2,5-dimethylfuran (DMF) as a potential liquid transportation fuel. Pd nanoparticles supported on N-containing and N-free mesoporous carbon materials were prepared, characterized, and applied in the hydrogenolysis of HMF to DMF under mild reaction conditions. Quantitative conversion of HMF to DMF was achieved in the presence of formic acid (FA) and H2 over Pd/NMC within 2 h. The reaction mechanism, especially the multiple roles of FA, was explored through a detailed comparative study by varying hydrogen source, additive, and substrate as well as by applying in situ ATR-IR spectroscopy. The major role of FA is to shift the dominant reaction pathway from the hydrogenation of the aldehyde group to the hydrogenolysis of the hydroxymethyl group via the protonation by FA at the C-OH group, lowering the activation barrier of the C-O bond cleavage and thus significantly enhancing the reaction rate. XPS results and DFT calculations revealed that Pd2+ species interacting with pyridine-like N atoms significantly enhance the selective hydrogenolysis of the C-OH bond in the presence of FA due to their high ability for the activation of FA and the stabilization of H- .

A Rotavirus Virus-Like Particle Confined Palladium Nanoreactor and Its Immobilization on Graphene Oxide for Catalysis.

ABSTRACT: In this work, a new viral protein cage based nanoreactor was successfully constructed via encapsulating Tween 80 stabilized palladium nanoparticles (NPs) into rotavirus capsid VP2 virus-like particles (i.e. Pd@VP2). The effects of stabilizers including CTAB, SDS, Tween 80 and PVP on controlling the particle size of Pd NPs were investigated. They were further immobilized on graphene oxide (i.e. Pd@VP2/GO) by a simple mixing method. Some characterizations including FT-IR and XPS were conducted to study adsorption mode of Pd@VP2 on GO sheets. Their catalytic performance was estimated in the reduction of 4-nitrophenol (4-NP). Results showed that Tween 80 stabilized Pd NPs with the molar ratio of Pd to Tween 80 at 1:0.1 possessed the smallest size and the best stability as well. They were encapsulated into viral protein cages (mean size 49 ± 0.26 nm) to assemble confined nanoreactors, most of which contained 1-2 Pd NPs (mean size 8.15 ± 0.26 nm). As-prepared Pd@VP2 indicated an enhanced activity (apparent reaction rate constant k app = (3.74 ± 0.10) × 10-3 s-1) for the reduction of 4-NP in comparison to non-confined Pd-Tween80 colloid (k app = (2.20 ± 0.06) × 10-3 s-1). It was logically due to confinement effects of Pd@VP2 including high dispersion of Pd NPs and high effective concentration of substrates in confined space. Pd@VP2 were further immobilized on GO surface through C-N bond. Pd@VP2/GO exhibited good reusability after recycling for four runs, confirming the strong anchoring effects of GO on Pd@VP2.

Graphene Oxide-Supported Catalyst with Thermoresponsive Smart Surface for Selective Hydrogenation of Cinnamaldehyde.

In this study, a graphene oxide (GO)-based thermoresponsive smart catalytic material with a phase-transition temperature of approximately 37 °C was developed by growing poly( N-isopropylacrylamide) (PNIPAM) on GO sheets (i.e., GO-PNIPAM). The composite was characterized by Fourier transform infrared spectroscopy, N2 adsorption, thermogravimetric analysis, organic elemental analysis, differential scanning calorimetry, and X-ray photoelectron spectroscopy. GO-PNIPAM-supported Ru catalysts (i.e., Ru/GO-PNIPAM) were then prepared for cinnamaldehyde (CAL) hydrogenation. The influence of thermosensitive smart surface on the reaction was investigated. Results indicated that GO-PNIPAM exhibited the hydrophilic surface at 25 °C, which resulted in highly dispersed Ru nanoparticles on the composite. Afterward, the surface wettability of Ru catalyst was spontaneously changed to hydrophobicity at 70 °C that greatly improved CAL sorption on the catalyst in the reaction. The synergistic effect between Ru and GO-PNIPAM as well as the great adsorption ability to reactants on Ru/GO-PNIPAM jointly resulted in the enhancement of catalytic activity over it in comparison to that over GO-supported Ru catalyst (Ru/GO). Meanwhile, the hydrophobic surface of Ru/GO-PNIPAM at a high-temperature preferred C═O adsorption mode, yielding a higher cinnamyl alcohol selectivity than Ru/GO did.

Catalytic dechlorination of carbon tetrachloride in liquid phase with methanol as H-donor over Ag/C catalyst.

Catalytic hydrodechlorination of carbon tetrachloride (CCl4) is an effective measure to remove CCl4 due to its pollutant character. The dechlorination of CCl4 to dichloromethane (CH2Cl2) and chloroform (CHCl3) with a molar ratio of 3:2 was catalyzed by carbon-supported silver (Ag/C) catalyst in methanol solution. It was proposed from the catalytic results and characterization (X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy) data that, the chloride ion is abstracted from adsorbed CCl4 by Ag to form CCl3 and CCI2 radicals and silver chloride (AgCl), and meanwhile the dehydrogenation of methanol over Ag domains intrigues initial active Ag-H species and formaldehyde (HCHO); then the CCI3 and CCI, radicals are combined with Ag-H to generate reaction products (CHCl3 and CH2Cl2) and Ag, and the dehydrogenated product HCHO facilitates the regeneration of formed AgCl to Ag with formation of carbon monoxide and hydrogen chloride. The catalyst can be recovered and recycled, and there was no significant decrease in catalytic activity and selectivity after 4th recycling.